C#: Compute the sum of the three given integers

using System; // Import the System namespace which contains fundamental types and base classes
using System.Collections.Generic; // Import the System.Collections.Generic namespace for collections
using System.Linq; // Import the LINQ namespace for LINQ functionality
using System.Text; // Import the System.Text namespace for string manipulation
using System.Threading.Tasks; // Import the System.Threading.Tasks namespace for asynchronous operations

namespace exercises // Define a namespace called 'exercises'
{
    class Program // Define a class named 'Program'
    {
        static void Main(string[] args) // The entry point of the program
        {
            // Output the result of test function with different sets of three integers as arguments
            Console.WriteLine(test(4, 5, 7)); // Test with integers 4, 5, and 7
            Console.WriteLine(test(7, 4, 12)); // Test with integers 7, 4, and 12
            Console.WriteLine(test(10, 13, 12)); // Test with integers 10, 13, and 12
            Console.WriteLine(test(14, 15, 16)); // Test with integers 14, 15, and 16
            Console.ReadLine(); // Wait for user input before closing the console window
        }

        // Function definition of test function that takes three integers 'x', 'y', and 'z' and returns an integer
        public static int test(int x, int y, int z)
        {
            // Calls the fix_num method for each integer and returns the sum of fixed values
            return Program.fix_num(x) + Program.fix_num(y) + Program.fix_num(z);
        }

        // Private method fix_num that takes an integer 'n' and returns a fixed integer or 0
        private static int fix_num(int n)
        {
            // Checks if 'n' falls within certain ranges and returns 0 if it does, otherwise returns 'n'
            return (n > 9 && n < 13) || (n > 13 && n < 17) || (n > 17 && n < 21) ? 0 : n;
        }
    }
}